The mission was launched when intelligence showed that Dr Dilip Joseph was in "imminent danger of injury or death", NATO's International Security Assistance Force said in a statement.

Joseph was abducted on December 5 by Taliban insurgents in the Surobi district of Kabul province.

"Today's mission exemplifies our unwavering commitment to defeating the Taliban," said General John Allen, the commander of US and ISAF forces in Afghanistan.

"I'm proud of the American and Afghan forces that planned, rehearsed and successfully conducted this operation. Thanks to them, Dr Joseph will soon be rejoining his family and loved ones."

Joseph was now "undergoing evaluations", the statement said, without giving further details.

A security source said the doctor had been involved in building clinics in Afghanistan, but details of his capture were not immediately available.

An ISAF spokesman said the rescue had been launched when multiple intelligence sources indicated that he was in immediate danger.

"We felt we had to act now," he said.

Seven of the doctor's captors were killed in the operation, which involved combined US and Afghan forces, he said.

He gave no further details of where the doctor had been held or on the rescue operation itself, saying they could be announced later in the day.

Surobi outside Kabul had been under the control of French troops until April this year, when responsibility for security was handed to Afghan forces as part of France's accelerated withdrawal from the country.

France ended its combat mission in Afghanistan last month, two years before allied nations contributing to the 100,000-strong US-led NATO force are due to depart.

Westerners are a prize target for the Taliban Islamists, who have waged an 11-year insurgency since being toppled from power in a US-led invasion in 2001.

In June, NATO special forces rescued two foreign women working for a Swiss-based charity who had been kidnapped and held in a cave in Afghanistan's remote and mountainous Badakhshan province, killing five of their captors.